A trade-off exists among various performance attributes that has been a major hurdle in the development of new polyethylene product technologies. Among such performance attributes are a combination of stiffness, toughness, processability and optical properties, all of which are important for most of linear low density polyethylene (LLDPE) film applications. However, it is difficult to achieve all of these attributes in one composition; improving toughness often reduces processability, increasing stiffness may cause optical properties to suffer. It is believed that such trade-offs in performance attributes can be significantly overcome by careful tailoring of molecular weight and comonomer distribution in the product. The inventors here have taken the approach to develop a unique polyethylene design via mixed-catalyst systems and proper screening of the product therefrom. More specifically, what has been found is that the use of two metallocene catalysts aimed at the so-called broad orthogonal composition (or comonomer) distribution (BOCD) space—the combination of low weight average molecular weight (Mw) and low short chain branching (SCB) (high density) population of polyethylene chains with high Mw and high SCB (low density) population—achieves the best combination of desirable performance attributes.
Background references include WO 2014/099307, WO 2015/123164, U.S. Pat. Nos. 6,875,828; 7,256,239; 7,504,055; 7,576,166; 9,371,441; US 2013/167486; EP 2 621 969 A, KR 101485566 B1, and KR 101288500 B1.